1. Field of the Invention
The invention relates to the field of pipeline repair, specifically low pressure gas line repair without service interruption.
2. Description of the Related Art
Previously, gas line repairs involved expensive and labor-intensive excavation of the gas line for replacement. Insitu gas line repair via insertion of a pipeline lining as described in British Gas plc U.S. Pat. No. 6,056,016 enables sealing via relining of a length of straight piping, but does not enable sealing or repairing of fittings creating bends in the flow path, such as the connections of the supply line to the gas main which could be, for example, a tap and elbow. The current invention solves this problem.
The invention apparatus and method are designed to allow a sealant spray coating to be applied to the inside surface of a gas main tap and/or elbow without requiring excavation of the surrounding area. Exposure of the operator to gas is minimal through the use of locking techniques so that the line, while not shut off, may have various tools inserted into it, including the spray head for applying a coating to the inside of the target area of the piping. Nitrogen is used to inflate a sealing bladder once the line has been tapped, allowing change-over from the residence supply gas and metering pipe assembly to a sealing assembly. A polyethylene hose is fed into the pipe. Within the polyethylene hose is a smaller nylon hose whose end is a steering spray head attached to a spring, the spring being rotatable via the nylon hose to allow feeding through any obstacles in the line all the way into the gas main. The steering spray head has nozzles in it through which, while it is rotating, the sealant may be applied, the rotation and spray pattern allowing complete coverage of the inside of the target pipe area. Nitrogen is also used to pressure pump the sealant down the line to the target area.